This study foccuses on accidents associated with ammonia and refrigeration.
On Monday around 8 am, a technician detected an odour of mercaptan (foul-smelling gas at < 1 ppb, toxic at high concentrations) in the dialkyl zinc dithiophosphate (ZDDP) unit of a chemical plant producing additives for lubricants. He was sampling a product scheduled for transfer since the previous Saturday in the adjustment tank when the tank's "high temperature" alarm went off in the control room. Around 9 am, analyses confirmed that the product had thermally decomposed. An inerting test conducted by adding a zinc oxide / water mix failed near 11 am due to technical difficulties that slowed preparation of the neutralising mix within a mobile mixer; namely by lack of an outlet connection, insufficient time allotted for mix preparation. Given the saturation of the unit's scrubber, foul-smelling cloud drifts beyond the site. The plant operator activated the internal emergency plan at 10 am and informed the Prefecture around 11:30; 33 municipalities were notified thanks to the phone alarm system. Other neutralisation tests conducted at the end of Monday evening also failed. Wind direction had changed; the odours spread throughout the county, then the Paris Metropolitan area and the southern part of England during the night. Tens of thousands of individuals felt discomforted, some complaining of vertigo, headaches and vomiting. Emergency services performed some 20 medical visits in and around Rouen. The Prefect assembled a public information team as of Tuesday morning and, as a precaution, activated the external emergency plan at 10:35 am Tuesday. From Wednesday morning through Friday evening, a new operating protocol allowed "safe" neutralisation of the decomposing product in batches of 12 and 36 tonnes prior to truck transfer to an incineration facility. According to a conservative assessment, this decomposition generated 95 kg of H2S, discharged via the stack of the scrubber system, and another 545 kg of mercaptans not entirely treated (accounting for a maximum discharge into the atmosphere of 272 kg). Given the geographic spread of the malodorous plume, this accident received heavy media attention both in France and abroad. Once the tank had been cleaned, the external measures were lifted on 6th February. Operating losses were initially estimated at several hundred thousand Euros due to plant shutdown for the duration of the incident and a ZDDP production line still idle 3 months later. Several causes were identified: - On Friday 18th January, a technician inadvertently started the adjustment tank stirrer and not the recirculation pump on the unit's control panel. Transferred to the tank on Saturday morning, a product batch at 94°C gradually heated until Monday morning, when the thermal decomposition was discovered (T > 110°C). Technicians on their rounds that weekend had not noticed the stirrer running despite the indicator light on the control panel and the shaft visibly rotating at the top of the tank; - The filling of a storage tank, combined with limited demand, led the operator to store product in an adjustment tank, whose transfer and recirculation mechanisms were only operable in manual mode following the implementation Friday of a software safety step that deact [...]>
During his shift, an employee of a special chemical products plant noticed at 1:20 pm a release of white smoke through the vents on an intermediate storage tank containing acrylic acid (AA, C3H4O2, flammable and corrosive substance, boiling point: 141°C). The tank (70 m³, 75 mm stainless steel shell) had been filled in preparation for a distillation column filling test; moreover, it was heat insulated and inerted with nitrogen. The employee sounded the alarm; a crew of internal fire-fighters attempted to stop the exothermic polymerisation rea [...]
At a Seveso-classified plant producing substances used in medical imaging, a temperature control defect on a biconical dryer caused product decomposition during the drying cycle. The subsequent pressure surge led, around 10 pm, to the explosion of part of the glass piping (a pipe elbow connecting the dryer to its vacuum pump). At the time, the dryer was holding 1,800 kg of a mix containing ethanol and an product releasing iodine (I2), hydrochloric acid (HCl) and nitrogen oxides (NOx) when decomposing. I2 was discharged into the atmosphere via b [...]
An explosion occurred around noon while conducting hot work (with a disc saw) on a 320-m³ fixed-roof tank at a pharmaceutical plant employing 240 personnel. The tank cover was blasted 20 m away and the subcontractor performing cutting works was killed. Three other subcontractors and a plant employee were severely burnt and injured by the shock wave. Notified by neighbours and not by the operator, fire-fighters arrived on the scene 15 min after the explosion and promptly extinguished the fire. Municipal and provincial authorities as well as Reg [...]